Just because you're a middle class non-minority doesn't mean you should have trouble writing about yourself. I think that's a misconception that everyone has, that you have to talk about trials and tribulations or overcoming adversity. I can't tell you what to write about because i don't know you, but there has to be something about yourself that sticks out or that was like an "ah hah" moment when you knew you want to go to law school. Even WASP (White Anglo-Saxon Protestants) can write a good PS, don't sell yourself short.